Photo Vocab #1: Crop Factor

Photo Vocab #1: Crop Factor

Lenses are categorized according to their focal length, which is the guide to their angle of view or magnifying ability. But in modern DSLRs this is affected by the size of the sensor, and there are many different sensor sizes now. In order the address this makers also quote an equivalent focal length, or a ‘crop factor’.

Most digital SLRs use an APS-C size sensor that’s smaller than full-frame 35mm negative film stock. Most lenses made for DSLRs use a design intended for use on 35mm SLRs as well. They have a ‘crop factor’ of approximately 1.6x so that when you fit a 35mm lens to a DSLR, its ‘effective’ focal length is 1.6x the categorized zoom of the lens, which is around 52mm.

It required a little bit of math on your part, unless you invest in a Full-Frame DSLR which sports an image sensor that is 35mm in size, thus eliminating the math you might have to do. It’s an important consideration especially in you’re moving from film SLRs over to DSLRs.